Reip(ing) riak node created two copies in the cluster

Nitish Sharma sharmanitishdutt at gmail.com
Wed May 2 13:04:18 EDT 2012


On May 2, 2012, at 6:12 PM, Jon Meredith wrote:

> Hi Nitish, for this to work you'll have to stop all the nodes at the same time, clear the ring on all nodes, start up all nodes, then rejoin
> 
> If you clear the rings one node at a time, when you rejoin the nodes the ring with the old and new style names will be gossipped back to it and you'll still have both names.
Sorry for the confusion. I didn't clear the rings one node at a time while keeping other nodes live. Following are the steps I followed:
1. Stop Riak on all the nodes.
2. Remove ring directory from all nodes.
3. Start the nodes and rejoin.

> I didn't realize you had a large amount of data - originally you said "Currently, we are hosting limited amount of data", but 200mil docs per node seems like a fair amount.  Rebuilding that size cluster may take a long time.
> 
Yeah, we are currently serving very limited amount because of Riak shortage. In total, we have almost 750 million documents served by Riak.
> Your options as I see them are
>   1) If you have backups of the ring files, you could revert the node name changes and get the cluster stable again on riak at IP.  The ring files have a timestamp associated with them, but we only keep a few of the last ring files, so if enough gossip has happened then the pre-rename rings will have been destroyed.  You will have to stop all nodes, put the ring files back as they were before the change and fix the names in vm.args and then restart the nodes.
> 
>   2) you can continue on the rebuild plan.  stop all nodes, set the new names in vm.args, start the nodes again and rebuild the cluster, adding as many nodes as you can at once so they rebalance at the same time.  When new nodes are added the claimant node works out ownership changes and will start a sequence of transfers.  If new nodes are added once a sequence is under way the claimant will wait for that to complete, then check if there are any new nodes and repeat until all nodes are assigned.  If you add all the nodes at once you will do less transfers over all.
> 
> 
> If the cluster cannot be stopped, there are other things we might be able to do, but they're a bit more complex.  What are your uptime requirements?
> 
We have currently stopped the cluster and running on small amount of data. We can wait for the partition re-distribution to complete on Riak, but I don't have a strong feeling about it. "member_status" doesn't give us a correct picture: http://pastie.org/3849548. Is this expected behavior? I should also mention that all the nodes are still loading existing data and it will take few hours (2-3) until Riak KV is running on all of them.

Cheers
Nitish
> Jon
> 
> 
> 
> On Wed, May 2, 2012 at 9:57 AM, Nitish Sharma <sharmanitishdutt at gmail.com> wrote:
> Hi Jon,
> Thanks for your input. I've already started working on that lines. 
> I stopped all the nodes, moved ring directory from one node, brought that one up, and issued join command to one other node (after moving the ring directory) - node2. While they were busy re-distributing the partitions, I started another node (node3) and issued join command (before risk_kv was running, since it takes some time to load existing data).
> But after this, data handoffs are occurring only between node1 and node2. "member_status" says that node 3 owns 0% of the ring and 0% are pending.
> We have a lot of data - each node serves around 200 million documents. Riak cluster is running 1.1.2.
> Any suggestions?
> 
> Cheers
> Nitish
> On May 2, 2012, at 5:31 PM, Jon Meredith wrote:
> 
>> Hi Nitish,
>> 
>> If you rebuild the cluster with the same ring size, the data will eventually get back to the right place.  While the rebuild is taking place you may have notfounds for gets until the data has been handed off to the newly assigned owner (as it will be secondary handoff, not primary ownership handoff to get teh data back).  If you don't have a lot of data stored in the cluster it shouldn't take too long.
>> 
>> The process would be to stop all nodes, move the files out of the ring directory to a safe place, start all nodes and rejoin.  If you're using 1.1.x and you have capacity in your hardware you may want to increase handoff_concurrency to something like 4 to permit more transfers to happen across the cluster.
>> 
>> 
>> Jon.
>> 
>> 
>> 
>> On Wed, May 2, 2012 at 9:05 AM, Nitish Sharma <sharmanitishdutt at gmail.com> wrote:
>> Hi,
>> We have a 12-node Riak cluster. Until now we were naming every new node as riak@<ip_address>. We then decided to rename the all the nodes to riak@<hostname>, which makes troubleshooting easier.
>> After issuing reip command to two nodes, we noticed in the "status" that those 2 nodes were now appearing in the cluster with the old name as well as the new name. Other nodes were trying to handoff partitions to the "new" nodes, but apparently they were not able to. After this the whole cluster went down and completely stopped responding to any read/write requests.
>> member_status displayed old Riak name in "legacy" mode. Since this is our production cluster, we are desperately looking for some quick remedies. Issuing "force-remove" to the old names, restarting all the nodes, changing the riak names back to the old ones -  none of it helped.
>> Currently, we are hosting limited amount of data. Whats an elegant way to recover from this mess? Would shutting off all the nodes, deleting the ring directory, and again forming the cluster work?
>> 
>> Cheers
>> Nitish
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>> riak-users at lists.basho.com
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>> 
>> 
>> 
>> -- 
>> Jon Meredith
>> Platform Engineering Manager
>> Basho Technologies, Inc.
>> jmeredith at basho.com
>> 
> 
> 
> 
> 
> -- 
> Jon Meredith
> Platform Engineering Manager
> Basho Technologies, Inc.
> jmeredith at basho.com
> 

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